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| United States Patent |
5,636,077
|
|
Kim
|
June 3, 1997
|
Automatic power-saving circuit for video recording/reproducing apparatus
Abstract
In a video recording/reproducing apparatus, an automatic power-saving
circuit determines the existence of an input video signal and controls
recording/reproducing functions accordingly, whereby recording/reproducing
functions continue if an input video signal is present, and, if no video
signal exists and no function key is input for a predetermined period of
time, the recording/reproducing actions are halted and power is
automatically cut-off.
| Inventors:
|
Kim; Hyo-sung (Seoul, KR)
|
| Assignee:
|
Samsung Electronics Co., Ltd. (Kyungki-do, KR)
|
| Appl. No.:
|
414116 |
| Filed:
|
March 31, 1995 |
Foreign Application Priority Data
| Current U.S. Class: |
360/69; 360/74.4; 386/46 |
| Intern'l Class: |
G11B 015/18 |
| Field of Search: |
360/69,60,33.1,74.1,74.4,71
358/335
369/6,7
386/46
|
References Cited
U.S. Patent Documents
| 4317189 | Feb., 1982 | Fukuoka | 369/7.
|
| 4319286 | Mar., 1982 | Hanpachern | 360/33.
|
| 4717968 | Jan., 1988 | Painton et al. | 360/69.
|
| 4991025 | Feb., 1991 | Eigeldinger | 360/33.
|
| 5138464 | Aug., 1992 | Park | 360/33.
|
| Foreign Patent Documents |
| 107925 | Jun., 1985 | JP | 369/6.
|
Primary Examiner: Psitos; Aristotelis
Assistant Examiner: Faber; Alan
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
Claims
What is claimed is:
1. An automatic power-saving circuit a video recording/reproducing
apparatus comprising:
a key input unit for entering a user command;
a power unit for supplying power to each element of the video
recording/reproducing apparatus;
a pre-amp for amplifying an input video signal and detecting and outputting
an envelope of the amplified signal;
a video signal discriminator for discriminating the existence of the input
video signal from the envelope signal output from said pre-amp and
outputting a discrimination signal according to said existence; and
a microcomputer for controlling said power unit according to said
discrimination signal and said user command.
2. An automatic power-saving circuit according to claim 1, wherein said
video signal existence discriminator discerns the existence of an input
video signal by discriminating a control signal recorded on a track.
3. An automatic power-saving circuit according to claim 1, wherein said
video signal existence discriminator discerns the existence of an input
video signal by discriminating a vertical synchronizing signal.
4. An automatic power-saving circuit according to claim 1, wherein said
microcomputer halts video processing operations of the video
recording/reproducing apparatus and causes said power unit to cut-off
power when said video signal existence discriminator discriminates that
there is no input video signal present and no user command is input via
said key input unit for a predetermined amount of time.
5. An automatic power-saving circuit in a video recording/reproducing
apparatus comprising:
a key input unit for entering a user command;
a power unit for supplying power to each element of the video
recording/reproducing apparatus;
a pre-amp for amplifying an input video signal and detecting and outputting
an envelope of the amplified signal;
a video signal discriminator for discriminating the existence of the input
video signal from the envelope signal output from said pre-amp and
outputting a discrimination signal according to said existence;
a microcomputer for controlling said power unit according to said
discrimination signal and said user command; and
wherein said signal discriminator comprises:
a biasing circuit having first and second resistors connected to first and
second potentials, respectively;
a first transistor having a base connected to the biasing circuit and
receiving the envelope signal output from the pre-amp, a collector
connected to the first potential, and an emitter connected to a second
potential through a third resistor;
a second transistor having a base connected to the emitter of the first
transistor through a fourth resistor, a collector connected to the first
potential through a fifth resistor, and an emitter connected to the second
potential through a sixth resistor;
a third transistor having a base connected to the emitter of the second
transistor through a seventh resistor, a collector connected to the first
potential, and an emitter connected to the second potential through a
ninth resistor; and
an integrating circuit having a capacitor connected between the emitter of
the second transistor and the second potential, an eighth resistor
connected between the emitter of the second transistor and the emitter of
the third transistor, and a tenth resistor having one terminal connected
to the emitter of the third transistor and a second terminal supplying the
discrimination signal.
6. A method for automatically cutting-off power to a video
recording/reproducing apparatus, comprising the steps of:
determining if a video signal is present;
outputting a cut-off signal if a key input is not present during a
predetermined amount of time while said video signal is not present; and
cutting-off power output from a power unit of the video
recording/reproducing apparatus based on the cut-off signal;
wherein said determining step comprises the steps of:
discriminating the presence of an envelope signal output from a pre-amp of
the video recording/reproducing apparatus; and outputting a logic signal
having a first level if the envelope signal is discriminated, and having a
second level if the envelope signal is not discriminated.
7. A method according to claim 6, wherein said step of outputting a cut-off
signal comprises the steps of:
detecting a logic signal indicating the absence of the video signal;
starting a counter for determining an elapse of the predetermined period of
time upon detecting the logic signal which indicates the absence of the
video signal;
detecting a key input; and
generating the cut-off signal upon the counter indicating the elapse of the
predetermined time period and no key input being detected.
8. A method according to claim 7, wherein said step of detecting the logic
signal detects a transition in logic levels of the logic signal to
indicate the absence of the video signal.
9. A method according to claim 7, wherein said step of detecting the logic
signal detects a logic level of the logic signal to indicate the absence
of the video signal.
10. A method according to claim 6, wherein said step of determining if a
video signal is present comprises the steps of:
determining if a pre-amp of the video recording/reproducing apparatus
outputs an envelope signal; and
outputting a logic signal having a logic "high" level if the envelope
signal is output.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an automatic power-saving circuit for a
video recording/reproducing apparatus. More particularly, it relates to an
automatic power-saving circuit for halting a recording or reproducing
operation and automatically cutting-off power when no input video signal
is present and no function key has been depressed for a predetermined
amount of time.
Generally, when a video signal is reproduced from a recording medium by a
video recording/reproducing apparatus for home use, such as a
videocassette recorder or camcorder, the apparatus reads out information
written to the recording medium through a pickup, and then outputs a video
signal after processing the information in a video signal processor. In
the case of recording a video signal onto a recording medium, a video
signal provided from a television or external video signal source is
processed for recording.
In a conventional home-use video recording/reproducing apparatus, when a
video signal is reproduced from a recording medium such as a magnetic tape
or is recorded onto a recording medium, the reproducing or recording
operation continues for a period of time. The length of the period of time
depends on the recording/reproducing speed mode (i.e., SP, LP, SLP etc.)
and the tape length, and extends until the end of the tape is detected by
an end sensor. The recording/reproducing operation continues regardless of
whether or not a video signal is present. Such a needless continuation of
the recording/reproducing operation, when no video signal is present,
consumes excessive power. Moreover, the friction between the tape and
head, as well as other factors, causes unnecessary wear and system fatigue
and, thus, shortens the lifetime of the apparatus.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to
provide an automatic power-saving circuit which halts a recording or
reproducing operation and automatically cuts-off power when an input video
signal is determined not to exist and when no input from a function key is
received for a predetermined period of time.
Accordingly, to achieve the above object, there is provided an automatic
power-saving circuit in a video recording/reproducing apparatus
comprising: a key input unit for entering a user command; a power unit for
supplying power to each element of the video recording/reproducing
apparatus; a pre-amp for amplifying an input video signal and detecting
and outputting an envelope of the amplified signal; a video signal
discriminator for discriminating the existence of the input video signal
from the envelope signal output from the pre-amp and outputting a
discrimination signal according to the existence of the video signal; and
a microcomputer for controlling the power unit according to the
discrimination signal and the user command.
Further, the present invention relates to a method for automatically
cutting-off power to a video recording/reproducing apparatus, comprising
the steps of: determining if a video signal is present; outputting a
cut-off signal if a key input is not present during a predetermined amount
of time while said video signal is not present; cutting-off power output
from a power unit of the video recording/reproducing apparatus based on
the cut-off signal.
BRIEF DESCRIPTION OF THE DRAWINGS
The above objects and advantages of the present invention will become more
apparent by describing in detail a preferred embodiment thereof with
reference to the attached drawings in which:
FIG. 1 is a block diagram illustrating an automatic power-saving circuit in
a video recording/reproducing apparatus according to the present
invention;
FIGS. 2A and 2B are views showing waveforms of the output signal of the
pre-amp shown in FIG. 1;
FIG. 3 shows a circuit according to an embodiment of the video signal
existence discriminator shown in FIG. 1; and
FIG. 4 is a flowchart illustrating the operation of the microcomputer shown
in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an automatic power-saving circuit in a video
recording/reproducing apparatus according to the present invention in
which the video recording/reproducing apparatus is a videocassette
recorder.
The circuit shown in FIG. 1 is comprised of a key input unit 30 for
entering user commands and information, a power unit 70 for supplying
power to each element of the apparatus, a pre-amp 10 for amplifying a
video signal input via deck system 60 and outputting an envelope signal by
detecting the envelope of the amplified signal, a video signal existence
discriminator 20 for determining the existence of an input video signal
based on the envelope signal output from pre-amp 10 and outputting a
discrimination signal according to the determination, and a microcomputer
40 for controlling power unit 70 according to the discrimination signal
output from video signal discriminator 20 and according to the existence
of an input entered via key input unit 30.
FIG. 2A shows the waveform of an output signal from pre-amp 10 when an
input video signal is present at the output of pre-amp 10. FIG. 2B shows
the output signal waveform from pre-amp 10 when there is no video signal
present.
FIG. 3 shows a circuit according to an embodiment of the video signal
existence discriminator shown in FIG. 1.
The circuit shown in FIG. 3 is comprised of a transistor Q.sub.1 having a
base applied with an output signal of pre-amp 10, a collector applied with
a power voltage (Vcc), and an emitted connected to ground via a resistor
R.sub.3. Resistors R.sub.1 and R.sub.2 are connected to the base of
transistor Q.sub.1, and act as bias resistors for transistor Q.sub.1. The
circuit is further comprised of a transistor Q.sub.2 having a base and
emitter connected, respectively, to the emitter of transistor Q.sub.1 via
a resistor R.sub.4 and to ground via a resistor R.sub.6, and a collector
which is applied with the power voltage (Vcc) via a resistor R.sub.5. The
circuit also includes a transistor Q.sub.3 having a base and emitter
connected, respectively, to the emitter of transistor Q.sub.2 via a
resistor R.sub.7 and to ground via a resistor R.sub.9 and whose collector
is applied with the power voltage (Vcc). Also, a resistor R.sub.8 is
connected between the emitters of transistors Q.sub.2 and Q.sub.3, a
capacitor C.sub.1 is connected to ground from the emitter of transistor
Q.sub.2, and a resistor R.sub.10 is connected between the emitter of
transistor Q.sub.3 and a first input of microcomputer 40.
FIG. 4 is a flowchart for explaining the operation of microcomputer 40
shown in FIG. 1. Steps 100 to 120 constitute a video signal existence
discrimination process for discriminating the existence of a video signal
written on a magnetic tape, from an envelope of the video signal
reproduced from the magnetic tape. Steps 130 to 150 constitute a key input
detection process for detecting the existence of a key input from key
input unit 30 and for performing the corresponding function thereof, when
it is determined that no video signal is written on the magnetic tape.
Steps 160 to 200 comprise an automatic power-saving process for
automatically cutting-off power after a predetermined time has elapsed in
which no video signal is present.
Operation of the preferred embodiment of the present invention is described
in detail as follows, referring to FIGS. 1 to 4.
Pre-amp 10 amplifies a signal reproduced, for example, from a magnetic tape
loaded in deck system 60 through a pickup (not shown) during a
reproduction operation, and generates and outputs an envelope signal to
video signal existence discriminator 20. Pre-amp 10 generates the envelope
signal by detecting an envelope of the amplified signal. Here, deck system
60 may be a single or double deck. If an input video signal exists, an
envelope signal, as shown in FIG. 2A, for example, is output. If the input
video signal does not exist, a "zero" level DC signal as shown in FIG. 2B,
is output.
Video signal existence discriminator 20 discerns the existence of an input
video signal by referring to the envelope signal output from pre-amp 10.
The video signal existence discriminator 20 outputs a logic signal to
microcomputer 40 indicating the determined existence of an input video
signal.
Next, the operation of video signal existence discriminator 20 is explained
in detail, referring to FIG. 3.
Transistor Q.sub.1 acts as a buffer and amplifies the voltage and current
of the envelope signal output from pre-amp 10, as shown in FIGS. 2A and
2B, and applies the amplified result to the base of transistor Q.sub.2 via
resistor R.sub.4. Here, resistors R.sub.1 and R.sub.2 operate as biasing
transistors. Transistor Q.sub.2 amplifies the signal output from
transistor Q.sub.1 and applies the amplified signal to the base of
transistor Q.sub.3 via resistor R.sub.7. Capacitor C.sub.1 integrates the
signal output from transistor Q.sub.2, to control the switching of
transistor Q.sub.3. When an envelope signal output from pre-amp 10 exists,
the charge current across capacitor C1 switches transistor Q3 to output a
logic "high" via its emitter to microcomputer 40. However, when the
envelope signal does not exist, transistor Q.sub.3 outputs a logic "low"
to microcomputer 40
Accordingly, microcomputer 40 controls servo 50 and power unit 70 according
to the existence of a video signal and a key input. The operation of
microcomputer 40 is explained below with reference to the flowchart shown
in FIG. 4.
In step 100, microcomputer 40 sets a video recording/reproducing apparatus
into an appropriate mode, such as a recording or reproducing mode. In step
110, the existence of an input video signal is determined by detecting a
logic state transition in the output from video signal existence
discriminator 20 which is applied to microcomputer 40. If no such signal
transition is present in step 110, which implies that a video signal
exists, the process returns to step 100 and operation continues. On the
other hand, if a transition is detected, which indicates that the input
video signal is no longer present, a timer inside microcomputer 40 is
started in step 120. The internal timer counts to a predetermined time,
irrespective of reproducing speed of the videotape.
In step 130, the existence of input from key input unit 30 is discriminated
while the internal timer counts to measure the elapse of the predetermined
time, in step 120. When a key input exists, the internal timer is turned
off in step 140, and then the function associated with the key input is
performed in step 150. If the key input does not exist, the existence of
an input video signal is again determined in step 160 by detecting a
transition of the output signal of video signal existence discriminator
20. If such a transition is detected in step 160, which indicates that an
input video signal now exists, the process returns to step 100, via step
170 where the internal timer is turned off, and the reproducing or
recording operation continues. On the other hand, if no such transition is
detected, which indicates that the input video signal is still not
present, the internal timer is checked in step 180 to determine whether
the predetermined time has elapsed, based on the timer's counting. If the
predetermined time has not elapsed, the process returns to step 130, and
if it has elapsed, the internal timer is turned off in step 190 and power
unit 70 cuts-off power in step 200. Here, the predetermined time (for
example, three to ten minutes) can be set by the user or preset by the
manufacturer.
That is, basically, during a reproducing operation in a videocassette
recorder, the end of a video program recorded on a magnetic tape is sensed
by detecting an envelope signal output from pre-amp 10, and then, if no
user command is input via key input unit 30 for a predetermined period of
time, the reproducing operation in the videocassette recorder is halted
and power unit 70 is automatically cut-off.
While steps 110 and 160 are described above in terms of detecting a
transition in the output of video signal existence discriminator 20, other
methods of detecting a change can be used. For example, a particular logic
level of the output can be detected to indicate the presence or absence of
a video signal, such as a logic "high" indicating that the video signal is
present, and a logic "low" indicating that the video signal is not
present.
In the aforesaid embodiment, the detailed configuration, operation and
effect of an automatic power saving method performed during reproduction
in a videocassette recorder are described. However, it is self-evident
that the same effect as described above is obtainable whether a recording
operation is performed for recording an input video signal supplied from a
standard videocassette recorder, camcorder or television, or for recording
onto a recording media using one side of a double-deck videocassette
recorder.
Also, in the aforesaid embodiment, an envelope signal of a video signal
output from a pre-amp is used for detecting the existence of an input
video signal. However, in the case of a VHS-type apparatus, a control
signal to be recorded on a track or a vertical synchronizing signal or
video output signal can be used for such a purpose with the same effect.
As described above, in an automatic power-saving circuit of a video
recording/reproducing apparatus according to the present invention, during
video processing operations such as recording or reproducing, operation
continues if an input video signal is determined to be present by
discriminating the existence of an input video signal. If no such input
video signal exists and no input from a function key is received for a
predetermined period of time, the video processing function is halted and
power is automatically cut-off. Therefore, the automatic power-saving
circuit has an effect of avoiding unnecessary power consumption and
protects against excessive wear of the apparatus.
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